In many communication systems, carrier frequency offset (CFO) may appear at a receiver due to a mismatch between a carrier frequency of a received signal and a local oscillator frequency of the receiver. Since CFO can adversely affect receiver performance, CFO estimation and correction algorithms may need to be employed to provide satisfactory performance from the receiver.
OFDM is sometimes used as a modulation scheme in wireless communication systems such as, by way of non-limiting example, wireless local area networks (WLAN), fixed wireless access, digital audio broadcasting (DAB), and digital video broadcasting (DVB). A desirable aspect of OFDM is that relatively simple equalization can be achieved in an OFDM receiver. This makes OFDM desirable in wireless applications with changing channel conditions. OFDM also benefits from efficient implementations of the fast Fourier transform (FFT) that can be used to modulate and demodulate the transmitted data.
To improve decoding accuracy of OFDM receivers, synchronization and channel estimation algorithms may be used. Synchronization generally includes estimation of the CFO, symbol timing of the received data, carrier phase offset, and sampling rate offset.
The CFO can have adverse effects on the performance of a system. The signal-to-noise ratio can be adversely affected when the CFO is smaller than an OFDM subcarrier bandwidth. If an integer part of the normalized CFO, which can be defined as the CFO normalized to the subcarrier bandwidth, is greater than one, then a cyclic shift of the subcarriers will occur at the receiver.